Invasive species in non-native ecological systems and environments often results in overpopulation of that species such that the native species and ambient environment is thrown out of balance. The invasive species may out-compete native species for food and shelter, and may not have any natural predators to keep non-native populations in check. Once an invasive species is introduced into a non-native environment, the non-native species may quickly repopulate the area, drastically shifting the ecological balance and system. For these reasons, vast resources are invested each year in efforts to eliminate invasive plant and animal species in the United States and abroad. Previous control methods vary whether the species is microbial, animal, or plant.
The control and elimination of invasive aquatic animal species is done by methods including, for example, physically catching and removing the animals, sterilization, building mechanical barriers, or treating the water chemical dispersions, toxic bait, or various pesticides. The control of invasive aquatic plants is done, for example, by mechanical harvesting, manual removal, and chemical spraying. Each of the aforementioned methods of control and removal of invasive species has limitations in use and problems and associated with it. Some of the problems include the propagation and increase of pollutants, environmental and ecological damage, great cost, low efficiency, and overall ineffectiveness.
Shipping carries more than 80% of the world trade and in the process 12 billion tons of ballast water per year. Ballast water is an essential part of ship operations, providing trim, stability, propeller immersion, and maintaining safe levels of hull stresses in various states of loading and unloading. However, invasive species are carried in vessel ballast water and introduced via discharge of ballast water. The globalization of trade, the rising tourism and the massive volume of cargo shipments have increased the chance of accidental introduction of invasive species. More than 10,000 species each day were estimated to be transported across the oceans globally in the ballast water of cargo ships. Many species are able to withstand the hardships of a journey across the seas. When the ship docks, unloads its cargo and empties its ballast tanks, the plants, animals, microbes are then unintentionally released into the new waters. Many of those species might successfully adapt into the new environments, outcompete native species and cause economic, social, recreational and ecological losses.
Shipping is widely considered one of the most important causes of anthropogenic changes to species distributions in the aquatic ecosystems, including oceans, rivers, lakes and the like. It is difficult to quantify the economic, ecological, recreational, and social losses caused by invasive species introduction via discharge of ballast water. Even further, the cost associated with losses such as the loss of native species and ecosystem functions are simply impossible to estimate. It is crucial to improve current ballast water management technology in order to reduce the economic, ecological, recreational and social losses caused by non-indigenous species introduction via discharge of ballast water.